The invention relates to a control system for an incineration plant, such as for instance a refuse incineration plant.
The invention relates to a control system for an incineration plant, such as for instance a refuse incineration plant, comprising an incineration furnace with an inlet for supplying material to be burned, an outlet for discharging burned material, a combustion path extending between the inlet and the outlet, and along which, in use, the material is transported in a direction of transport from the inlet to the outlet for combustion of the material, and air supply means for supplying air to the combustion path, the incineration plant further being provided with a steam generator for generating steam by means of heat generated in the furnace and control means comprising a steam controller and an oxygen controller which, depending on respectively the amount of steam generated by the steam generator and the amount of oxygen in the furnace, generate one or more control signals for adjusting the size and/or speed of a supply stream of the amount of material respectively to and through the furnace and/or for adjusting the amount of air supplied to the furnace by means of the air supply means, the control means adjusting the signals such that the steam generator generates an amount of steam per time unit which optimally corresponds with a first predetermined adjusting value, and that the air supply means supply such an amount of air that an amount of oxygen is contained in the furnace which optimally corresponds with a second predetermined adjusting value. Such a system is known from practice and is, inter alia, used in the refuse incineration plants built by the firm of Von Roll. One of the problems occurring during refuse incineration is constituted by the fluctuations in the process caused by the continuously changing refuse composition. Strong fluctuations in the refuse composition and thus in the energetic power supplied may result in strong process fluctuations, such as fluctuations in the temperature of the furnace. Such process fluctuations may be harmful to the plant. Also, the process fluctuations may involve product fluctuations, such as fluctuations in the amount of steam produced or the electricity generated therewith. This has the result that the yield and quality of these products is reduced. In the known control system, to provide a solution for the problems described, control means are used which generate the at least one control signal to adjust the size and/or speed of the stream of the amount of material through the furnace and/or to adjust the amount of air supplied to the furnace by means of air supply means. The control means serve to control the at least one control signal such that the above fluctuations are damped.
The known control means as used in the so-called Von Roll control reduce the above-described problems because the at least one control signal is formed as the sum of a signal provided by a steam controller and a signal provided by an oxygen controller, as a result of which excess oxygen in the furnace and deficient steam oppositely affect the control signal and therefore counterbalance each other to a certain degree as far as the control of the plant is concerned. Nevertheless, the known control system is not, or not sufficiently, capable of retaining the output variables steam and oxygen at the selected adjusting points.
There is therefore a need for an improved control system for an incineration plant. The object of the invention is to meet this need. According to the invention a control system of the above-described type is therefore characterized in that the output signal of the steam controller is supplied to a summing device for forming a sum signal used to modify via corresponding calculating means the output signals of control circuits controlled by the output signal of the oxygen controller for the air supply to the furnace and/or the size of the supply stream of material to the furnace and the speed of the stream of material through the furnace respectively, to obtain definitive control signals.